Kill Mobs, Escape, Aesthetics, Lives, "Lose"

-You can now "kill" mobs, hooray!
-Implemented the "Escape" exit key!
-Adding some aesthetics, enjoy :P.
-"Lives" are now implemented. Lose 1 for every 1 mob that gets to the
left side of the screen!
-You can "lose" when you lose all lives!
ToDo:
-Better graphics, if possible. Seems a bit odd.
-Upgrades?
-Maybe make the game screen larger.